1. Field of the Invention
The present invention relates to a metal-resin composite, a method for producing the metal-resin composite, a busbar, a module case, and a resinous connector part.
2. Description of Related Art
In the viewpoint of weight saving and protection of mechanism elements and electronic parts against severe usage environment, for example, many elements and parts using a resin are widely utilized as the elements and parts used for an automotive field. Generally, such an element and a part have a structure that a metallic member is integrated with a resin member, and are required to have high reliability for resisting a long-term usage, especially, to maintain adhesive strength between a metallic member and a resin member under high humidity and high temperature environment. In other words, a high adhesive property between the metallic member and the resin member has been demanded as a very important theme.
Such a method for highly adhering has been known, comprising the steps of roughening a surface of a metallic member and increasing an adhesive property thereof by the anchor effect. For example, the Japanese Laid-Open Patent Publication No. S63-160367 describes that a lead frame made of an iron-nickel alloy at a resin sealing part is electroplated with a tin-nickel alloy so as to have a plating thickness within the range from 10 to 15 μm and surface roughness within the range from 2 to 5 μm. Further, the Japanese Laid-Open Patent Publication No. H9-148508 describes that the whole surface of a lead frame body is electrolytically treated using the current density more than the critical current density in an electrolytic solution containing a specific metal ion thereby to form a rough layer, and further electrolytically treated using the current density less than the critical current density in an electrolytic solution containing a specific metal ion thereby to form a covering layer.
Further, as a method for highly adhering by roughening a surface through an etching process, such a method for adhering with high-intensity has been known, comprising the steps of etching copper or aluminum material in an aqueous solution containing water-soluble reduction agents such as iron (II) chloride or hydrazine or the like so as to roughen the surface of the metallic material, and having the resultant metallic material adhere to the resin member with high-intensity by the anchor effect.
However, the techniques disclosed in the Japanese Laid-Open Patent Publication Nos. S63-160367 and H9-148508 have the following drawbacks. That is, in the technique of the Japanese Laid-Open Patent Publication No. S63-160367, the surface roughness of the lead frame is relatively rough in the degree of several μm, which may require a plating thickness of 10 μm or more. Hereby, there are drawbacks that this technique may elongate the plating time thereby to reduce the productivity, or need the quite often supplement of a plating solution thereby to increase the production cost. Particularly, since the lead frame described in the Japanese Laid-Open Patent Publication No. S63-160367 contains iron, if such an iron based material is to be plated, the pre-treatment such as removal of grease and an oxidation film on the surface of the metallic member may have to be conducted, prior to the plating process. In other words, if such a pre-treatment is not conducted or insufficiently conducted, or if the surface of the metallic member is to be exposed to the air after the pre-treatment, the adhesive ability of the plating film formed after the plating process to the metallic member may decrease, resulting in probability that the plating film peels.
Further, in the technique described in the Japanese Laid-Open Patent Publication No. H9-148508, for example, if the metallic member contains a plurality of metal types, the optimal pre-treatment solution for forming a roughening layer and a covering layer is different depending on the metal types, resulting in difficulties in uniformly treating the surface of the metallic member. Therefore, the adhesive strength may be lowered corresponding to the regions of the surface of the metallic member. Moreover, the technique disclosed in the Japanese Laid-Open Patent Publication No. H9-148508 may have a drawback that the roughness layer or the covering layer may peel off, depending on whether the pre-treatment is performed or not, similarly to the drawback of the technique disclosed in the Japanese Laid-Open Patent Publication No. S63-160367.
Further, a method for highly adhering by roughening a surface through an etching process comprises a step of scraping off the surface of the metallic member by the etching process, which results in difficulties in improving the dimensional accuracy of the surface of the metallic member. Furthermore, the plating film may be removed in the etching process. Herein, since the etching solutions are different depending on the metal types, if the metallic member includes a plurality of metal types, this makes it difficult to uniformly treat the surface, similarly to the technique disclosed in the Japanese Laid-Open Patent Publication No. H9-148508, resulting in probability of creating regions where the adhesive strength lowers. Further, the surface of the metallic member thus obtained after the etching process becomes the ground metallic member itself. Accordingly, the metal types capable of improving the adhesive property by using the chemical interaction between the metallic member and the resin member may not be efficiently utilized.